$5.00 for that? Totally worth it.
There are a few differences between Oblivion and Skyrim. I haven't had the opportunity to play Skyrim since I picked it up, but from what I've heard the game has much more of a survivalist feel, and a decently hard game. The environments, people, creatures, AI, graphics, draw distance, that's all been improved. So expect from Oblivion a step back in terms of graphical and technological awe. The game is a lot easier, and in comparison to Skyrim the graphics are just cartoony.
But I'm painting you a bad picture with all that. The good of the game, oh there's so much. I know you're consumed by Skyrim, but you should put it down to put some serious time into Oblivion. Beyond the obvious benefit you'd get with story connection,
there's just so much to do . And obviously that goes for Skyrim as well, but you need to experience the amazing plots in Oblivion, the Dark Brotherhood, Shivering Isles, Thieves Guild, Knights of the Nine, and Mage's Guild being the best ones. Skip the other ones if you want, they're forgettable. Look up the story of the main plot, it's a let down.
But yeah, after all that rambling,
yes, get Oblivion, put down Skyrim, and play what the people on these boards still find things to post about 5 years after it's release